Abstract The impact of assistive device use (handrails, canes, etc.) on patient outcomes and rehabilitation is unknown. Consequently, clinicians must make a decision whether to encourage or discourage use during training without understanding the implications for patient outcomes. The objective of our research is to determine the impact of assistive device use during treadmill and overground walking post-stroke. As an initial step, this project will determine the effects on an individuals paretic-side propulsion, a commonly targeted variable in post-stroke gait rehabilitation. The aims of this study are to identify changes in propulsion with (1) handrail use during treadmill walking and (2) cane use during overground walking. We hypothesize that assistive device use will modify propulsion but that changes in propulsion, and how individuals achieve these changes, will depend on how the device is used (i.e. light or self-selected support). Furthermore, we hypothesize that the impact of assistive device use will vary as a function a subjects level of movement impairment. To assess our aims, subjects post-stroke will undergo gait analysis sessions with three-dimensional motion capture during treadmill (Aim 1) and overground (Aim 2) walking with different assistive device use conditions (no use, light support, and self-selected support) for a total of six walking conditions. Paretic-side propulsion (primary outcome) as well as key contributors to propulsion (secondary outcomes: paretic ankle moment, trailing limb angle, muscle activation and plantar flexor muscle function) will be analyzed across walking conditions to explore the kinematic and kinetic changes in gait dynamics as a result of assistive device use. Finally, we will determine the relationship between clinical assessments of function known to be related to assistive device use (self-selected walking speed, SIS Mobility) and changes in the primary and secondary measures of propulsion. By understanding the specific impact of assistive devices on propulsive force, a key variable in increasing walking function, clinicians can make informed decisions regarding assistive device use during rehabilitation for both patients that use assistive devices in their daily lives and those who do not.